Multiple laser cavity apparatus

ABSTRACT

A multiple cavity laser system includes: a controller configured to operate the system as well as a plurality of laser cavities, each of the laser cavities having an output end wherein, when activated by the controller, an output laser beam is emitted from the output end of each of the laser cavities. The output laser beams when activated are directed, either directly or indirectly, to a rotating mirror. The rotating mirror is operatively connected to the controller and a servo motor. The servo motor, under direction of the controller, redirects the output laser beams along a common optical axis and the output laser beams of the plurality of laser cavities are combined along the common optical axis.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority to U.S. ProvisionalPatent Application No. 61/978,046, filed Apr. 10, 2014. The completedisclosure of this application is hereby incorporated by referenceherein.

FIELD OF THE INVENTION

The present invention relates to laser apparatus suitable for surgicaland non-surgical applications in which a plurality of laser cavities areincorporated into a unitary housing.

BACKGROUND OF THE INVENTION

In one aspect, this invention relates to laser apparatus in whichmultiple laser cavities are contained within a unitary housing. Thelaser cavities may all be of the same type, power and wavelengths orthey may be of different power levels, wavelengths and types. One suchlaser apparatus is sold under the trademark VersaPulse by Lumenis ofYokneam, Israel. In the apparatus, four laser cavities are contained ina unitary housing. The outputs of the four laser cavities may becombined by using suitable mirrors and lenses so that the output is asingle laser beam which is the combined output of the four lasercavities. In the device, a 90 degree step-rotating mirror folds andcombines the four beams sequentially from the four laser cavities into acommon optical path. The device is also described generally in thefollowing US patents, all of which are herein incorporated in theirentirety by reference: U.S. Pat. Nos. 5,375,132, 5,659,563, 5,781,574,5,999,555 and 6.115.396. Of course, depending on the number of lasercavities and the housing in which the laser cavities are installed, the90 degree rotating mirror may be a lesser or a greater number ofdegrees. In this type device, the 90 degree step-rotating mirroroptically switches the laser outputs from the four cavities. Therelative position of the step-rotating mirror relative to each lasercavity defines the overlap-level of the laser beams along their commonoptical path. Ideally, all four laser beams are fully aligned into asingle and uniform common optical path without any offsets. However,since the step-rotating mirror is limited to 90 degrees steps only andsince the position of the four cavities is not precisely in exact 90degrees orientation to each other (for example, 90+/−0.5 degrees),aligning the step-rotating mirror to one cavity results in somemisalignment to the others. The above degree of uncertainty is theprimary reason of mutual misalignment of the four laser cavities.

The lasers are fired rapidly, the mirror must react and be able, as itrotates in steps, to combine all the beams so that a uniform, fullyoverlapped single beam is outputted from the apparatus. The four laserbeams are separated in time due to the rotating mirror but the opticalpath must be the same and aligned. In the above known device, prior tothe present invention, the alignment point of the step-rotating mirroractually averages the four optimal alignment points of each of the fourcavities. However, this may lead to a reduction in the overall combinedlaser beam output quality as a result of four slightly different opticalpaths

Turning now to FIG. 1, the figure shows a schematic of a multiple lasercavity apparatus. Although only two laser cavities are shown, this isdue to the perspective of the drawing. It can be seen that in aperspective orthogonal to the page that two additional laser cavitiescan be accommodated. As can be seen in FIG. 1, the laser cavities 10 and12 output two laser beams to an arrangement whereby each impinges onmirrors 14, 16, 18 and 20. Those mirrors then reflect the respectivelaser beam onto a rotating mirror 22 which is driven by a servo motorand position encoder 24. It is to the rotating mirror and positionencoder that the present invention is, in part, directed. The rotatingmirror, as can be seen in FIG. 1, then directs the two light beams b 26and 28 from, respectively, laser cavities 12 and 10 onto first andsecond mirrors 30 and 32 and eventually to output 34. The third andfourth cavities have similar optical paths like 10 and 12 and they alsocombine in the rotating mirror 30. Mirrors 30 and 32 are common for thefour laser beams from the four laser cavities. The beams are separatedin time not slightly. They are sequentially generated by the four lasercavities. The rotating mirror needs to arrive at the right position atthe right time to reflect the appropriate beam along the same opticalpath. If not so, the optical paths will differ from one another. Asafety shutter 36 is also included the light path as seen in FIG. 1, thepurpose of which will be discussed in greater detail below. Changes madeto the structure and operation of the servo motor mirror the servo motorand position encoder will be described below in the section entitled“Detailed Description” below.

In another aspect, apparatus such as described above which includesmultiple laser cavities or even a singular laser cavity require a sourceof power to charge the flash lamps such as 40 and 42. Conventionally, inknown devices this may be accomplished by charging one or more largecapacitors in a capacitor bank and rapidly discharging those capacitorsinto the flash lamps thus causing excitation of the laser rods 44 and 46as seen in FIG. 1. Existing systems and off-the-shelf lamp switches andIGBTs function well to “fast charge” these capacitor banks This providesthe ability to quickly charge already discharged capacitors from alow-energy state to a high energy state at a fast rate. However, thereis no off-the-shelf, easy solution to discharge. In normal practice, thepreference is to discharge the full energy from the capacitors and notto stop at some point in the discharge process. Power levels may rangefrom 20-150 watts or from 100-150 watts.

However, in many applications, it may be desirable for the operator of alaser apparatus such as, but not limited to, the above describedapparatus to change the pulse width from among: a short pulse, a mediumpulse and a long pulse. One aspect of the present invention is directedto a solution to allow rapid and controlled discharge of the capacitorbanks so that the pulse width may be rapidly changed and controlled bythe user through the user interface. A full explanation of the operationand structure of this aspect of the present invention will be found inthe “Detailed Description” below.

In yet another aspect, in known laser apparatus devices the lasercavities are cooled, usually by water. Allowing the laser to become toohot can cause overheating, faulty operation, decreasing laser efficiencyand even destruction of the laser cavity, all undesirable results. Inaddition, it is desirable that the laser apparatus operate in a normalambient room temperature and humid environment rather than aspecialized, climate-controlled environment. A specialized environmentrequired a sealed and controlled environment. It is another aspect ofthe present invention to create a laser system which is not sealed andin fluid communication with the ambient room environment. In knownsystems having laser cavities which are open to ambient room conditions,the water which is used to cool the laser cavities and the remainder ofthe laser apparatus is not actively cooled to avoid condensation.Ambient room temperature systems, having a volume of water large enoughto absorb the heat from the laser and through known heat exchangedevices and this is usually sufficient to keep the laser at normaloperating temperature. In contrast, sealed laser cavities may activelycool the water without risking damage to the cavity due to condensation.Laser energy absorption by condensed water, especially condensed wateron the laser rod and especially on the lasing side of the rod, maysignificantly harm the laser cavity. This is risk which is greatlyincreased with solid state lasers having high absorption coefficients inwater such as Holmium and the like having wavelengths higher than about1.5 microns. However, in order to operate, open cavity lasers such as inaccordance to one aspect of the present invention in other than idealambient temperature situations including high humidity situations,present non-active cooling systems may be insufficient to keep lasercavities at an ideal temperature in which they operate most efficientlyand potentially cause damage and/or destruction to the laser cavitiesdue to overheating. The main reason why this is not desirable is thedecreased in the output power due to the apparatus having to work athigher temperatures. Thus, there is a need for a more efficient, activecooling system to allow for cooling of the lasers in both ideal and notso ideal environments in an open cavity configuration. This aspect ofthe present invention is further described in the “Detailed Description”below.

In yet another aspect, one application of the above described laserapparatus is, by way of example only, applying the output of thecombined laser beams in the apparatus of the present invention to breakup kidney stones or stones in the bladder. Typically, this is done byoutputting the laser beam 34 of FIG. 1 through to a suitable opticalfiber which is threaded into the kidneys and or the bladder. The laseroutput beam travels from the output 34 through the optical fiber andexits at an optical fiber end within the bladder or kidney and is aimed,for example, at the stones to break them up. An aiming beam may also bepresent to allow the physician to accurately aim the ablation laser atthe desired target to be fragmented. Typically, the aiming beam may be a532 nm green aiming beam and the ablation beam may be a Holmium beam of2100-2112 nm. Also, there may be a need to provide an apparatus whichmay allow fast switching of the output laser state from a high energycutting/ablation state to a lower energy, coagulating state.

It is to the above aspects of the present invention that the below“Detailed Description” is directed.

SUMMARY OF THE PRESENT INVENTION

In an aspect, a multiple cavity laser system includes a controllerconfigured to operate the system; a plurality of laser cavities, each ofthe laser cavities having an output end wherein, when activated by thecontroller, an output laser beam is emitted from the output end of eachof the laser cavities. The output laser beams, when activated, aredirected, either directly or indirectly, to a rotating mirror. Therotating mirror is operatively connected to the controller and a servomotor. The servo motor, under direction of the controller, redirects theoutput laser beams along a common optical axis, wherein the output laserbeams of the plurality of laser cavities are combined along the commonoptical axis.

In a second aspect, the multiple cavity laser system includes X numberof cavities; the servo motor includes a position encoder; and whereinthe position encoder is directed by the controller to position therotating mirror to receive the output laser beams of the X number ofcavities as the rotating mirror is in line with the respective outputlaser beams.

In another aspect, the laser cavities are arranged with the cavitiesparallel to one another and the output ends are arranged at the same endof each of the laser cavities. The number of laser cavities is four.

In another aspect, the rotating mirror is positioned to receive theoutput of each of the plurality of laser beams when activated. One ormore mirrors are positioned to receive the output laser beams and directthe beams to the rotating mirror. One or more mirrors are positioned toreceive the output laser beams from the rotating mirror and direct thebeams to the common optical axis.

In yet another aspect, laser spots formed as an output of the pluralityof laser beams onto the rotating mirror are non-aligned and thecontroller directs the position encoder to calibrate the positions ofthe laser spots to determine and store the number of steps of theencoder to bring the laser spots into alignment.

In another aspect, the controller calibrates the plurality of lasercavities on an individual basis, whereby the controller adjusts theposition of the rotating mirror for each of the laser beams emitted byeach of the laser cavities.

In a further aspect, a safety shutter is provided which is selectivelyinsertable into the common optical axis under direction of thecontroller.

In another aspect, the controller stores the position encoder in linepositions for each of the cavities and controls the retrieval of the inline positions as the rotating mirror moves to cause the rotating mirrorto be in line with each of the when the output beams are activated. Thelaser cavities are arranged in a 2×2 orientation.

In yet a further aspect, a method of operating a multiple cavity lasersystem includes: providing a controller configured to operate thesystem; providing a plurality of laser cavities, each of the lasercavities having an output end wherein, when activated by the controller,an output laser beam is emitted from the output end of each of the lasercavities; providing a rotating mirror operatively connected to thecontroller and to a servo motor to which the output laser beams, whenactivated, are directed. In this arrangement, the servo motor, underdirection of the controller, redirects the output laser beams along acommon optical axis, whereby the output laser beams of the plurality oflaser cavities are combined along the common optical axis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic description of a known multiple cavity laserapparatus.

FIG. 2A is a schematic view of a light beam impinging on a rotatingmirror.

FIGS. 2B-2D illustrate characteristics of the rotating mirror tiltangle.

FIGS. 3A and 3B illustrate a user interface in connection with theapparatus of the present invention.

FIGS. 4A to 4F illustrate steps in the present invention to implement apulse width modification.

FIGS. 5A and 5B illustrate a user interface in two modes in connectionwith apparatus of the present invention to control lasing and suctioningmodes of operation.

FIG. 6 is a schematic view of an exemplary apparatus cooling system usedwith the apparatus of the present invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Rotating Mirror Control

As discussed above, a suitable mirror 22 and its motor and positionencoder 24 are used to direct the plurality of laser beams to a commonoutput at 34 in a way that each of the four laser beams is combined withthe others. Since the rotating mirror rotates to intercept each of thefour laser beams sequentially and then sends those beams to output 34,necessarily the beams will arrive at the output 34 at slightly differentbut still close times. In the existing system described herein, theservomotor provided only 90° fixed steps, given the example of fourlaser cavities arranged along the same axis in a 2×2 orientation. Thus,the servomotor 24 moves in four steps to cover all four cavities andthis action folded their beams into a common optical path with theoutput, as mentioned, at 34. During assembly, the rotating mirror can becalibrated relative to a first cavity. However, as to the other threecavities, a compromise of the relative location of the mirror the othercavities was needed since only 90° steps were available using servomotor24. In the present invention, the rotating mirror can make movements insmall steps and thus allow calibration of all four cavities both duringthe manufacture of the apparatus or when replacing defective cavities inthe field much more accurately then in the past. For example, theservomotor can be set to step from the first cavity to the second cavityby only, for example, 89.6° while then stepping 90.3° to the third. Byproviding this flexibility this improves the stability accuracy andoverlap of the four beams once folded into a combined optical path.Selection of a faster motor than the motor 24 shown in FIG. 1 allows thesystem to work at higher frequencies, in the range of 5-100 Hz.Additional frequencies may range from 40-100 Hz, or 50-80 Hz.Furthermore, the accuracy of the combined beam allows the output to bemore precise and aligned and to operate with smaller optical fiberdiameters, in the range of 200 to 230 μm. Other diameter ranges from100-500 um, 250-400 um and 200-300 um. This provides significantadvantages over known systems such as those described above.

Turning attention now to FIG. 2A, this figure shows a rotating mirror100 having a center point 110. A motor with the capabilities describedin the previous paragraph rotates the mirror 100 around its center point110 in a direction shown for example as arrow A around the center point110 and an axis perpendicular to the drawing figure. An incident beam,such as beam 26 or 28 of FIG. 1, coming from one of the laser cavities10 or 12 impinges upon rotating mirror 100 at point 120. Ideally, actuallaser spot 120 onto rotating mirror should coincide with center point110. Also, ideally, all four actual laser spots from each of the fourcavities should coincide irrespective of which laser the beam came from.However, misalignments cause the actual laser spot 120 and the otherlaser spots to fall off from the center point 110. If the system had theability to calibrate the beam with two degrees of freedom by moving therotating mirror along X and Y axis, it could calibrate the system byadjusting correlating to lines B-B′ along one dimension and by anotheradjustment along line B′-B in the second dimension. However, since thesystem has only one degree of freedom to control such alignment, thatis, the rotation of mirror 100 around its center point 110, the actualbeam spot 120 can only be moved by slightly rotating the mirror alongline C-C′ to its closest location to the center point 110 which is 120′.

The encoder 24 discussed above is operatively connected with thecontroller. In the present embodiment, there are four laser cavities.The controller has a memory of a known type which stores, for eachcavity, the position 120′ which is the closest point to the center 110that the laser spot for a particular laser cavity can approach. Once aparticular laser cavity has been activated, the controller will causethe encoder to move the mirror to spot 120′ for that particular lasercavity. Thus, there will be stored, for the four laser cavities in thepresent embodiment, four positions 120′ corresponding to the fourcavities. If there are more or less cavities than four, the number ofpositions 120′ stored in the memory of the controller will changeaccordingly.

The system then stores the number of steps necessary to bring each ofthe laser cavity beams to its individual optimized point 120′. It shouldbe noted that since each laser cavity is expected to have at least aminimum different orientation relative to the mirror than the othercavities, each cavity will have its own circle C-C′ along which the beammoves in its own closest point 120′. The above process may be followednot only during normal assembly of the multiple cavity apparatus butalso during laser cavity replacement. With the above-described controlover the rotating mirror, each cavity is aligned to the rotating mirrorseparately and, during operation, the controller of the system knowsexactly which adjustment needs to be given to the servomotor order tobring the mirror to the optimal location relative to be then activatedlaser cavity.

Furthermore, the rotating mirror, by means of which 4 laser beams arecombined into the same optical path, is tilted with respect to therotating axis that is the motor axis. The tilt is α₀≈4.22° as shown inFIG. 2B. Due to the limitations of motor position measurement systemsthere is always some uncertainty in the mirror position, which resultsin the beam deflection in the desired direction. The maximal angularerror of the mirror position depends on the resolution of the motorposition measurement device. As an example in the case of an opticalencoder, the amount of encoder lines, N=500, and could be evaluated as

$\beta = {\frac{2\pi}{N} = {0.72{^\circ}}}$

Note that this angle relates to the rotation around the motor axis.

It should be understood that such a rotation results not only in avariance of the angle α₀, but also outputs the reflected beam off theplane of the drawing. That's why two different angles α_(→) and α_(↑) inorthogonal planes have to be taken into consideration.

While rotating, the reflected beam follows a cone with a full planeangle of 4α₀ (2α₀—amplitude) as shown in FIG. 2C.

Both mentioned above angles (α_(→) and α_(↑)) may be considered as sinand cos—components of the reflected angle variations.

$\alpha_{\rightarrow} = {{2\alpha_{0}\cos \; \beta} \approx {2{\alpha_{0}\left( {1 - \frac{\beta^{2}}{2}} \right)}}}$α_(↑) = 2α₀sin  β ≈ 2α₀β

Appropriate beam deflections are

${\delta\alpha}_{\rightarrow} \approx {{2{\alpha_{0}\left( {1 - \frac{\beta^{2}}{2}} \right)}} - {2\alpha_{0}}} \approx {{- \alpha_{0}}\beta^{2}} \approx {{- 1.1} \times 10^{- 2}\mspace{14mu} m\; {Rad}}$δα_(↑) ≈ 2α₀β ≈ 1.8  m Rad

FIG. 2D graphically explains all mentioned above.

The fact that the rotating mirror is actually curved does not affect theresult, because it relates to the central beam.

It is clear that the larger deflection angle δα_(↑)≈1.8 mRad must betaken for further calculation. Assuming the focal length of focusinglens to be F≈33 mm one can evaluate the spot shift in the focal plane

Shift≈F×δα _(↑)≈59 μm

Once more, this is the maximal shift value in assumption that theencoder error is equal to its discrete level. The shift may be decreasedby using a more precise encoder with increased amount of encoder lines.Another way is to use a more precise encoding algorithm, such as usingseveral shifted clock series or to use a different more precise positionmeasurement device.

Limiting the maximal spot shift in the focal plane to the level of 8 μmone can calculate that the mirror positioning error must be less thanβ≈0.1°, which is derived from the design of the fiber, the fiber portand their tolerances.

Due to the use of the above-described rotating mirror control, smallerdiameter optical fibers in the range of about 200 um may be utilizedbecause of the more precise alignment of the plurality of beams from themultiple laser cavities into a single laser beam output. This has anumber of beneficial effects, including the ability to use lower profilefiber inserted into the patient's body. The precision of the servo motoralso allows the use of operation at higher frequency rates above 50 Hz,including up to about 80 Hz.

Fast Discharge of the Capacitor Bank

This aspect of the present invention is directed to the control of thepulse width of the laser beam emanating from output 34 shown in FIG. 1.This can be accomplished by changing the voltage on the capacitor bank,such as from about 850V to 650V or even to 550V. For example, a shortpulse width may be in the range of approximately 120 to 600 us. Themedium pulse width may be in a range of approximately 600 to 700 us andlong pulse width may be in the range of approximately 700 to 1600 us.The transition between the various pulses width regimes preferably maybe short enough not to cause annoying delays for the operator.

As shown in FIGS. 3A and 3B, these figures illustrate a user interfaceon a laser apparatus of the type described above which permits theoperator to quickly change the power regime and thus the laser-tissueinteraction regime. As can be seen in FIG. 3A, the user is given, on auser interface screen, a number of options, including the option to setup the pulse widths of two pulse modes (for example short pulse andmedium pulse) and other working parameters, such as energy level andfrequency. The other working parameters of each pulse mode may bepredefined by the manufacturer to allow the physician to make fastswitching during a procedure between the first predefined pulse mode anda second predefined pulse mode. By simply touching the user interfacescreen, or actuating a remote user interface device such as amulti-pedal footswitch, hand switch or the like, the physician cancause, on the fly, a change in pulse width and profile from, by way ofexample, a short pulse characterized with a set of working parametersassociated with tissue cutting, to a medium pulse characterized with aset of working parameters associated with tissue coagulating. In FIG.3B, in another view of the same user interface screen, the physician ispresented with a short, tissue-cutting pulse and a long,tissue-coagulating pulse. Alternatively, the physician could select thedesired outcome, for example, hemostasis, minimal retropulsion and thesystem would automatically select the desired parameters, including, thedesired pulse width. Once the physician has selected a long or medium orshort pulse, the system may cause a controller which has control overthe capacitor bank to deliver the appropriate pulse width. This may beaccomplished by providing an electronic circuit and a shutterarrangement which will discharge the charged capacitor bank by lasingwhile the shutter is on (so that no optical energy is outputted throughoutput 34), to the desired preselected energy level so that a long ormedium or short pulse, having preselected profiles of workingparameters, may be produced as a result further lasing while the shutteris off.

As described above with reference to FIG. 1, a safety shutter 36 may beinterposed along the unitary optical path prior to the laser beamreaching output 34. One reason for the presence of the shutter 36 in theknown device is that the shutter is used to warm the laser rods into thehigher temperatures suitable for operation by so-called “blind” lasing.In practice, the shutter is used to block undesired pulses, such aspulses which are not within the set user parameters for pulse energy. Inthe present invention, high energy pulses delivered at high frequenciesare used to discharge the capacitors. When activated (these pulses arenot in the set user parameters but are set, for example, by the systemdesigner), the shutter is “on” for “blind” lasing. In general, thedesire here is to maintain the laser rod at a constant temperaturethrough, in large part, the use of the active cooling system describedin the present invention below. The shutter arrangement, followed by atleast one damper, is designed to absorb the laser energy reflectedinternally from the shutter to the damper during the so-called “blind”lasing. In the present invention, this same shutter is used to controlthe discharge of the capacitor bank and to do so in a rapid fashion.Previous solutions and other solutions for rapid discharge may requiremore electronics, special discharging circuits and specialized switchesand IGBTs be utilized to provide for rapid discharge. Thus, undercontrol of the controller of the system, the laser beam will utilizethis shutter to absorb the energy reflected internally during “blind”lasing until the desired voltage decrease has been reached, at whichpoint the shutter is moved out of the optical path in the laser cavityallowed to discharge through the output 34. Thus, this provides a simplesolution to what was heretofore a complex problem and does so withoutthe addition of further hardware. According to one aspect of the presentinvention, all laser cavities can fire one after another for dischargingor only part of each of laser cavities. The challenge has been to dodischarging as fast as possible without heating the laser rod too muchwhich could cause damage to the laser rod.

Turning now to FIG. 4, this figure shows the sequence by which differentpulse widths can be delivered by the laser apparatus. In a first step(A), the operator sets in the interface of FIGS. 3A and 3B the desiredpulse profile (energy, frequency) and pulse width. Next, in step (B),the user presses an included right or left pedal to cause the device toproduce the desired pulse width for the laser beam. In the next step(C), the shutter 36 shown in FIG. 1 is moved into the optical path ofthe laser beam and as described above laser cavities are fired todischarge the capacitors to the desired level as noted in step (D) ofFIG. 4. Next, the laser apparatus is warmed up through the use of theshutter 36 and the so-called “blind” lasing in step (E). When thedischarge of the capacitor bank level has been reached, such as, by wayof example only, approximately 650V, in step (F) the shutter 36 is offor in an open non-occlusive position or removed from the optical laserpath and the lasers cause to fire with the desired in control pulsedwidth(s). Thus, by using an existing portion of the apparatus, pulsewidth may be controlled without the necessity of the use of orincorporation of further circuitry or other hardware.

System Temperature Control

As discussed above, known laser apparatus include devices for coolingthe laser cavities themselves as well as the overall apparatus toprevent overheating and possible damage to the laser cavities. Many ofthese cooling systems operate at ambient room temperature and do notemploy, as mentioned, active devices to cool the apparatus. However, itis known that cooling the laser cavity or cavities may be used toincrease the overall power output of the laser cavity. Since the lasercavities such as shown in FIG. 1 are vacuum sealed, this will permitactive cooling of the system without risking undue condensation may harmthe laser cavity or other elements within the apparatus. In particular,with the use of Holmium laser device, which the laser beam is highlyabsorbable of water, water condensation on the laser rod within thelaser cavity may cause the rod to explode. Vacuum sealing cavities andoptical benches are both expensive and complex. A new design of thepresent invention permits the building of a cooling system which is anopen system but as well cooling the laser with an active chiller whichalso avoids condensation. An exemplary cooling systems which may be usedwith the present invention is illustrated in FIG. 6 of the drawings.

There are usually temperature and humidity sensors contained within thecavity. Based on the outputs of the sensors, the dew point in thecavity/ambient room may be calculated. Once the dew point has beencalculated, the controller within the system controls a cooling systemaccordingly. The system ensures that the working temperatures are highenough and far enough from the dew point to ensure that no condensationoccurs. Therefore, for example, if the room calculated dew point is 25°C., lasing can begin without turning on the active chiller but only bycirculating cooling water which is still at room temperature. Thisavoids condensation. In another example, if the calculated dew pointbased on the room conditions is 8° C., then active cooling can begin sothat the water is cooled down to a temperature which is above the dewpoint and this in turn increases the efficiency of the laser poweroutput. The desire is that the laser rod should work at as low aspossible temperature, however a too low temperature which is below thedew point may cause condensation which, as struck above, may cause harmor destruction of the laser cavity. An additional benefit of activecooling is that by actively controlling the temperature of the laserapparatus, the power output of the laser apparatus can be controlled andhigher power levels generated at lower temperatures, thus providingincreased output from the laser cavities without the need of additional,relatively expensive laser equipment.

Control of Lasing with Suctioning

As described above, one of the problems associated with the use of laserfibers within the human body is the presence of blood and otherdisintegrated stone or other debris interfering with the view of thephysician to control and direct the laser beam and have a good view ofthe target area. A suitable handpiece which may be used with a laserfiber is described in U.S. provisional application Ser. No. 61/927,426,filed Jan. 14, 2014 and assigned to the assignee of the presentinvention, the entire contents of which are herein incorporated byreference. The foregoing device described in the above applicationdiscloses a laser device which includes a suction module in a handpieceto allow the physician to not only apply laser energy to a target tissuebut also to activate a suction function which is provided the samehandpiece.

As shown in FIGS. 5A and 5B, a physician may be provided a userinterface which allows the physician to set the suction to a number ofdifferent modes. In FIG. 5A, for example, the suction is set to aso-called “auto mode” and in FIG. 5B, the suction is set to a so-called“on mode”. There also may be provided a so-called “off mode”. The “onmode” and “off mode” speak for themselves: in the “off mode” suction isnot turned on at all. In the “on mode” suction is always on. However, inthe “auto mode”, the controller of the system will activate the suctionfunction during the application of laser energy. The amount ofsuctioning applied may be either adjusted manually by the physician toany level, including one or more preset levels, or may be automatic inaccord with the set laser parameters, the energy per pulse delivered,the rate of repetition of the pulses applied, etc. This has the effectof clearing the area around the laser fiber tip so that any blood orstone debris is cleared from the physician's view while applying thelaser energy, allowing a physician to better see the target stone orother object.

Thus, it may be seen that utilizing the precision servomotor control aswell as incorporating the active cooling system above-described thesystem can reach high energy output levels in the range of 120 to 140 W.

While aspects of the present invention have been discussed inconjunction with a four laser cavity apparatus, it is clear that manyaspects may be used on lasers with less than or more than four cavities,including a single laser cavity. For example, the rotating mirror andmotor may be incorporated in any multiple laser cavity system or in anyoptical system in which precise mirror control is desired. The systemfor fast discharge of a capacitor bank may be used with other lasersystems or even with non-laser systems such as systems using incoherentlight. The system temperature control described in the present inventionlikewise may be used with other laser or non-laser apparatus. Thelasering/suction control apparatus may likewise be utilized in otherlaser surgical or non-surgical systems.

What we claim is:
 1. A multiple cavity laser system comprising: acontroller configured to operate the system; a plurality of lasercavities, each of the laser cavities having an output end wherein, whenactivated by the controller, an output laser beam is emitted from theoutput end of each of the laser cavities; the output laser beams whenactivated being directed, one of directly or indirectly, to a rotatingmirror; the rotating mirror being operatively connected to thecontroller and a servo motor; the servo motor, under direction of thecontroller, redirecting the output laser beams along a common opticalaxis, wherein the output laser beams of the plurality of laser cavitiesare combined along the common optical axis.
 2. The multiple cavity lasersystem of claim 1, wherein: the plurality of laser cavities is given asX number of cavities; the servo motor includes a position encoder; andwherein the position encoder is directed by the controller to positionthe rotating mirror to receive the output laser beams of the X number ofcavities as the rotating mirror is in line with the respective outputlaser beams.
 3. The multiple cavity laser system of claim 2 wherein thelaser cavities are arranged with the cavities parallel to one anotherand the output ends arranged at the same end of each of the lasercavities.
 4. The multiple cavity laser system of claim 3 wherein thenumber of laser cavities is four.
 5. The multiple laser cavity system ofclaim 3 wherein the rotating mirror is positioned to receive the outputof each of the plurality of laser beams when activated.
 6. The multiplelaser cavity system of claim 1 further comprising one or more mirrorspositioned to receive the output laser beams and direct the beams to therotating mirror.
 7. The multiple laser cavity system of claim 6 furthercomprising one or more mirrors positioned to receive the output laserbeams from the rotating mirror and direct the beams to the commonoptical axis.
 8. The multiple cavity laser system of claim 5 wherein atleast one of the plurality of laser spots formed as an output of theplurality of laser beams onto the rotating mirror is non-perfectlyaligned with the center of the rotating mirror and wherein thecontroller is configured to direct the position encoder to move themirror to the optimal position so that each laser spot from each of thelaser spots on the rotating mirror are the closest positions to thecenter of the rotating mirror
 9. The multiple cavity laser system ofclaim 8 wherein the controller includes a memory operatively associatedwith the controller, the memory storing, for each laser cavity, theoptimal position of each laser spot closest to the center of therotating mirror.
 10. The multiple cavity laser system of claim 1,further comprising a safety shutter selectively insertable into thecommon optical axis under direction of the controller.
 11. The multiplecavity laser system of claim 2 wherein the controller stores theposition encoder in line positions for each of the X number of cavitiesand controls the retrieval of the in line positions as the rotatingmirror moves to cause the rotating mirror to be in line with each of theX number of cavities when the output beams are activated.
 12. Themultiple cavity laser system of claim 4 wherein the laser cavities arearranged in a 2×2 orientation.
 13. The multiple cavity laser system ofclaim 2, wherein the system operates in a range of frequencies fromabout 40 to about 100 Hz, preferably in a range of about 50 to about 80Hz.
 14. The multiple cavity laser system of claim 2, wherein the systemoperates in a range of frequencies of about 5 to about 100 Hz.
 15. Themultiple cavity laser system of claim 2, wherein the system operateswith laser fiber diameters of 100 um to 500 um, preferably 250-400 umand most preferably from 200-300 um.
 16. The multiple cavity lasersystem of claim 2, wherein the system operates with laser fiberdiameters of 200-230 um.
 17. The multiple cavity laser system of claim2, wherein the system operates at power levels ranging from 20-150watts, preferably 100-150 watts.
 18. A method of operating a multiplecavity laser system comprising: providing a controller configured tooperate the system; providing a plurality of laser cavities, each of thelaser cavities having an output end wherein, when activated by thecontroller, an output laser beam is emitted from the output end of eachof the laser cavities; providing a rotating mirror operatively connectedto the controller and to a servo motor to which the output laser beams,when activate, are directed; wherein, the servo motor, under directionof the controller, redirects the output laser beams along a commonoptical axis, whereby the output laser beams of the plurality of lasercavities are combined along the common optical axis.
 19. The method ofclaim 13, wherein: the plurality of laser cavities is given as X numberof cavities; the servo motor includes a position encoder; and whereinthe controller directs the position encoder to position the rotatingmirror to receive the output laser beams of the X number of cavities asthe rotating mirror is in line with the respective output laser beams.20. The method of claim 13 further comprising the step of positioningrotating mirror to receive the output of each of the plurality of laserbeams when activated.
 21. The method of claim 13 further comprising oneor more mirrors positioned to receive the output laser beams and todirect the beams to the rotating mirror.
 22. The method of claim 16further comprising one or more mirrors positioned to receive the outputlaser beams from the rotating mirror and to direct the beams to thecommon optical axis.
 23. The method of claim 13 laser spots formed as anoutput of the plurality of laser beams onto the rotating mirror arenon-aligned and wherein the controller directs the position encoder tocalibrate the positions of the laser spots to determine and store thenumber of steps of the encoder to bring the laser spots into alignment.24. The method of claim 13 wherein the controller calibrates theplurality of laser cavities on an individual basis, whereby thecontroller adjusts the position of the rotating mirror for each of thelaser beams emitted by each of the laser cavities.
 25. The method ofclaim 13 wherein the controller stores the position encoder in linepositions for each of the cavities and controls the retrieval of the inline positions as the rotating mirror moves to cause the rotating mirrorto be in line with each of the cavities when the output beams areactivated.